Rimless Spectacle Lens Connection via Interference Fit
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Solution Overview
Problem
Conventional lens connectors for rimless spectacles face challenges such as relative movement or 'shaking' due to loose fits, occupy excessive lens area, and are difficult to manufacture and assemble, primarily due to limitations in the rotary cutting method used for producing connecting holes.
Innovation Solution
The method involves using a linear motion cutting technique with a specially designed forming tool to create a 'Smallest Form Locking Lens Connecting Hole' (SFLCH) with a round segment and narrow rectangular slots, allowing for an interference fit and secure connection without damaging the lens, and using a plug with a non-circular cross-section to prevent rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a clearance fit or transitional fit is used between the plug and connecting hole, then the lens can be manufactured using conventional rotary cutting methods, but relative movement or shaking occurs between the plug and lens
Solution Approach 1:
The patent changes the fit parameter from clearance fit or transitional fit to interference fit. This is achieved by making the plug's outer diameter slightly larger than the connecting hole's inner diameter, creating an interference fit that eliminates relative movement and shaking while maintaining manufacturing feasibility through precise control of the interference amount
Solution Approach 2:
The patent introduces non-circular slots into the connecting hole, creating an asymmetric geometry. The plug corresponds with this asymmetric shape, forming a form-locking joint that prevents rotational movement. This asymmetric design allows the connection to achieve both translational and rotational stability simultaneously
2Stability of the object's composition
If a form locking joint with non-circular plug and slot is used, then rotational movement is prevented, but the connecting hole production by rotary cutting method cannot accurately copy the plug's shape causing lens crack risk
Solution Approach 1:
The patent carefully controls the interference fit parameter, making the plug's outer diameter only slightly larger than the connecting hole's inner diameter. This controlled interference allows the non-circular shape to be achieved without excessive cutting forces that would cause lens cracks, while still providing sufficient form-locking capability to prevent rotation
3Reliability
If two points fixing method is used, then relative movement is prevented, but the connector occupies bigger area on the lens and is more difficult to manufacture and assemble
Solution Approach 1:
The patent extracts the second fixing point from the design, transitioning from a two-point fixing system to a single-point fixing system. The single plug with non-circular slot provides both translational and rotational constraint functions that were previously distributed across two separate fixing points, simplifying the overall connector structure and assembly process
Data Source
AI summary
A method for assembling a rimless spectacle has acts of forming multiple circular through holes in a lens of the rimless spectacle, forming two cavities respectively at two ends of a diameter of each through hole to form a non-circular connecting hole in the lens with a forming tool and assembling multiple connecting elements to the lens. Each connecting element has a plug securely connected to and held in one of the connecting holes in the lens. The plug has a non-circular cross section corresponding to the shape of the corresponding connecting hole and is slightly bigger than the corresponding connecting hole. In the assembling the connecting elements to the lens, the plug on each connecting element is forced to pressed into and be securely held in the corresponding connecting hole.